We tested the drug-susceptibility of 112 strains of Streptococcus pneumoniae isolated from various clinical materials since January 1975 to May 1976, and observed the changes of susceptibility of this pathogen. All strains tested remained very sensitive to benzylpenicillin and cephaloridine, but 59.8% of strains were resistant to tetracycline and 44.7% to chloramphenicol, and about 90% of chloramphenicol-resistant strains were also resistant to tetracycline. The percentage of resistant strains to tetracycline or chloramphenicol is increasing. Cross-resistance between tetracycline and doxycycline or chloramphenicol and thiamphenicol was observed. On this time we found three strains resistant to macrolides. Two of these strains were resistant to erythromycin, josamycin, oleandomycin, spiarmycin, mydecamycin, lincomycin, clindamycin and tetracycline, but one was resistant to josamycin, spiramycin, mydecamycin and chloramphenicol.